1. Field of the Disclosure
The subject disclosure relates to systems and methods for oil and gas drill strings, and more particularly to improved systems and methods for providing contactless, low maintenance downhole electrical transmission.
2. Background of the Related Art
In drill strings, hundreds of sections of drill pipe and associated downhole tools are connected in series. Many of these components require electrical continuity to transmit power, signals, and/or data. However, providing electrical transmission to the components can be challenging because various components not only rotate independently but may even rotate continuously and/or at different speeds. For example, a mud motor typically has upper and lower portions that rotate at different speeds. For another example, common control units have a roll-stabilized platform kept geostationary while an associated collar rotates at drill bit speed.
If electrical connection is desired between such components, the electrical connections must be capable of conducting or transmitting electrical power, signals, and/or data between independently and even continuously rotating or otherwise moving structures. Further, downhole tools are operated under harsh conditions. Thus, the connections must be designed robustly to maintain reliability under mechanical stress, misalignment and abusive mishandling.
In view of the above, several approaches have been developed to provide electrical connections in drill strings. Commonly, slip rings with wiper rings are used to transmit signals across moving parts, see for example U.S. Pat. No. 7,074,044 issued on Jul. 11, 2006. Other approaches have utilized conductive rings paired with brushes affixed to electrode plates, see for example U.S. Pat. No. 6,089,875 issued Jul. 18, 2000. Still other approaches involve inductive coupling devices or the creation of oil environments with pressure compensators and rotating seals.
There are problems associated with the techniques of the prior art to accomplish electrical connections in drill strings. The prior art approaches are quite complex and require difficult maintenance. The complex nature tends to make the connections unreliable under the extraordinarily harsh conditions. Additionally, frequent and difficult maintenance makes the connections far less than economic. There is a need, therefore, for improved systems and methods which require minimal maintenance with a simple structure that assures effective electrical connections.